Disable and Enable submit button in jquery

This is answered in the jQuery FAQ

How do I disable/enable a form element?
There are two ways to disable/enable form elements.

Set the 'disabled' attribute to true or false:

 // Disable #x
 $('#x').attr('disabled', true);
 // Enable #x
 $('#x').attr('disabled', false);

Add or remove the 'disabled' attribute:

 // Disable #x
 $("#x").attr('disabled', 'disabled');
 // Enable #x
 $("#x").removeAttr('disabled');

Update: Now the way to do it (as said by FAQ) is only:

// Disable #x
$( "#x" ).prop( "disabled", true );

// Enable #x
$( "#x" ).prop( "disabled", false );

Use .prop() method and use the $(this) to reference the target element within the callback function

jQuery(function($) {

  const $register = $("#register"),
        $loading = $("#loading");

  $register.on("click", function() {
  
    $(this).prop('disabled', true);
    $loading.show();
    
    setTimeout(function() {
      $register.prop('disabled', false);
      $loading.hide();
    }, 2000);

  });

});

<input id="register" value="Register" type="submit">
<div id="loading" style="display:none;">Wait 2 sec...</div>


<script src="//code.jquery.com/jquery-3.1.0.js"></script>